The technical field in which this invention resides is that of millimeter-wave solid state oscillators and, more particularly, to the coupling of such oscillators to millimeter-wave transmission systems, and to accomplish this with minimum impedance mismatch and, consequently, maximum power transfer of transverse electromagnetic mode waves generated in such resonating cavity oscillators into TEM waveguides, microstrip transmission lines and the like wave conductive elements.
In the copending applications of Horn et al entitled "Image Line Voltage Controlled Oscillator With Replaceable Components", Ser. No. 679,971 and "An Integrated Varactor Tuned Coaxial Gunn Oscillator For 60 GHz Operation", Ser. No. 679,974 both filed Dec. 10, 1984, Gunn oscillator devices are shown for the generation of millimeter-wave energy outputs, with the outputs being finally controlled by ancillary electronically tuned oscillator devices. In both of these disclosures, the mode of take-off for the generated energy wave is through a wave-conductive element which is mounted atop and close to one end of the resonating cavity of the solid state mechanically tuned oscillator, preferably using a Gunn diode. In such known arrangements, while the normally acceptable limits of coupling efficiency are available, optimum power transfer is lost because the connection point for the wave guide coupling into the oscillator cavity is removed from the zone of maximum electrical field strength of the wave which is generated. The prior art, then, in general, shows arrangements where power takeoff of generated waves from oscillator devices in this technology normally involves the takeoff at some random point at or near the end of the resonating coaxial cavity of the oscillator element used in the device. There has, up to the time of the present invention, been no discernable effort to maximize the power transfer by effectively locating the point of transfer between the millimeter-wave generating apparatus and the transmission line, or its link from the oscillator element into a transmission line.
The presently known and used millimeter wavelength type oscillators generally use high frequency oscillator elements as their main source of wavelength generation. These devices find particularly suitable applications in radar and communications circuits. In the frequency ranges of interest, that is to say 35 GHz to about 300 GHz, low R.F. power levels are the general rule. The relatively high operating frequencies and related short wavelengths of the outputs require extremely precise construction of the oscillator physical parts. For these reasons, it is extremely important to minimize power loses between the various discretely discernible portions and circuit elements of such arrangements. In order to benefit from the relatively high stability of mechanically tuned diode units such as the Gunn oscillator, it is advantageous to precisely as possible match the elements used as connections and translation modes into other parts of the circuit. It is therefore understandably desirable to provide a fixed type maximum power transfer point for translation of the generated wave into its next medium or transmission step.
With this then being the state of the art, we conceived and developed our invention with the principal object of providing a maximum power transfer method and apparatus for matching Gunn diode outputs with transmission line microstrips.
A further object of the invention is to provide a method and apparatus for the maximum power transfer with minimum impedance mismatch of a Gunn diode output to a microstrip line by means of a fixed probe extending from the microstrip line into the oscillator resonating coaxial cavity zone of maximum electric field strength with respect to the energy wave being generated therein.
A further and important object of the invention is to provide a method of translating the millimeter-wave energy output developed in the resonating cavity of a Gunn oscillator into a millimeter-wave transmission line, not only with maximum power transfer, but without any significant change of mode from the transverse electromagnetic mode of the generated wave with the transverse electromagnetic propagation mode in the transmission line.
The apparatus and system of our invention has found particularly advantageous utilization in the realization of these objectives and purposes.